Invasive Species: Emerald Ash Borer. Saving Ash Trees, One Decoy at a Time

Here's the bad news: The emerald ash borer (EAB), the highly invasive insect from Asia that has been found in 24 states, half the U.S., is no dummy. 

The ash borer, Agrilus planipennis, which kills ash trees by feeding below the bark, cutting off vessels that conduct water and nutrients through the arboreal systems, can rarely be drawn in by entomologists' attempts to fool males with  "decoy" versions of female EABs that they included on traps. In order to monitor, contain or eradicate the bugs, scientists aim to lure them into traps, according to a release from Penn State.

That said, researchers might have found one way--via biomimetic fabrication (a method that imitates the engineering methods of nature) of two molds of a female EAB, which is stamped onto a plastic sheet to form a decoy--to get the longer-lasting attention of male EABs, according to the release.

Typically, males approach females above, looking for sunshine reflecting off the female's green carapace. When green plastic bugs have been placed in the traps, males quickly recognize the falsehood and buzz off, according to Eurekalert. 

After trying 3-D printing and failing to ensnare the males, entomologists realized that the insects are looking for the fine structure of the elytra, the hardened fore-wing of the insect. Then the researchers tried using a biomimetic fabrication of a negative die and a positive die, using those to stamp the decoys on a plastic sheet. Biomimetic just means imitating models, systems, and elements of nature in order to solve complex human problems--one example is that Vel-Cro is a biomimetic version of burrs found in fields. Then the researchers cut out and painted the decoys first black, then metallic green, according to the release.

Essentially, the lures produced using dies were 40 percent more successful in drawing male EABs than dead females were, said said Akhlesh Lakhtakia, Charles Godfrey Binder Professor in Engineering Science and Mechanics, Penn State, according to the release. 

At that point, it became necessary to speed up production. The scientists made a negative die or mold from 10 euthanized female EABs instead of one, then placed a heat-curing plastic in the mold. They heated the plastic to cure it, then cut and painted the lures. They reported their results recently in the Journal of Bionic Engineering.

Going up against the voracious EABs will still be a challenge, but the researchers are hoping to save new ash trees. "When we began in 2010, the idea was so that we could wipe out the invasive species with these lures," said Lakhtakia in the release. "We now realize we cannot get rid of them, they have spread over half the country. However, because the species feeds exclusively on ash, once those trees are gone from an area, the insects move on. Perhaps we can use the lures to protect new ash trees planted in that area." 

Follow Catherine at @TreesWhales